1. Field of the Invention
The present invention relates, in general, to methods and systems for determining the acceptability of signal data and, in particular, to methods and systems for determining the acceptability of signal data collected from prothrombin time test strips.
2. Description of the Related Art
Typical monitoring systems for the measurement of a fluid sample characteristic include a device, such as a portable hand-held meter, and a test strip (e.g., a prothrombin time [PT] test strip) to which a fluid sample (e.g., a whole blood sample) is applied. The device and test strip are used in tandem to measure an analyte concentration (e.g., blood glucose concentration) or other characteristic (e.g., prothrombin time and/or International Normalization Ratio [INR]) of the fluid sample. The device typically measures a property or properties of the test strip (e.g., an optical reflectance, optical transmittance, optical absorption or an electrochemical property) and then employs an algorithm(s) to calculate the characteristic based on the measured property or properties.
A variety of conventional prothrombin time (PT) monitoring systems that can be employed to measure the blood-clotting time (i.e., prothrombin time) of a user's whole blood sample are known to those skilled in the art. Such conventional PT monitoring systems are described in, for example, U.S. Pat. No. 6,261,519 and U.S. Pat. No. 6,084,660, each of which is hereby fully incorporated by reference, and European Patent Application EP 0974840. These conventional PT monitoring systems are typically used by laypersons using prescription anticoagulants, such as Warfarin, to monitor their oral anticoagulation status.
Conventional PT monitoring systems can require the use of external control solutions to validate prothrombin time and/or INR test results generated by the system. Such validation is necessary to avoid erroneous results due to, for example, the use of PT test strips that have been exposed to deleterious environmental conditions (e.g., elevated temperatures and/or humidity). In this regard, PT test strips that have been exposed to extreme, although not necessarily deleterious, environmental conditions are referred to as “stressed” PT test strips.
Result validation utilizing external control solutions is based on laboratory quality control methodology, wherein results obtained with the external control solutions are assumed to mimic the performance of a user's fluid samples. However, careful attention must be paid to the matching of control solution and reagent lot numbers, and the proper control of storage and use conditions for this assumption to hold true. Unfortunately, laypersons may misunderstand or overlook the consequences of mixing lot numbers, improper storage or improper use conditions. Such misunderstandings and oversight can complicate attempts to validate the results generated by a conventional PT monitoring system. Furthermore, many users perceive the external control solutions, which require multiple preparation steps and complicated training, as difficult to employ.
Still needed in the field, therefore, are an accurate method and system for determining the acceptability of signal data obtained from a prothrombin time (PT) test strip. The method and system should be able to determine if the signal data are unacceptable due to, for example, exposure of the PT test strip to deleterious environmental conditions (e.g., elevated temperature and/or humidity). The method and system should also be capable of being integrated into a portable hand-held mater in a simple fashion.